JPA / Hibernate加入常量值

Z时代
2024-01-10
分类：问答

我正在尝试使用join语句中的常量值从同一表中加入不同实体。在SQL中，我会做这样的事情…

SELECT *
FROM owner o
JOIN types t on t.owner_id = o.id AND t.type = 'A'
--                                ^^^^^^^^^^^^^^^^ THIS IS WHAT I AM TRYING TO REPLICATE

在Java + JPA / Hibernate中，我正在尝试执行以下操作…

@Entity
@Table(name = "OWNER")
public class Owner {
    @Id
    @Column(name="ID")
    private Long id
    @OneToOne(mappedBy = "owner", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumns({
        @JoinColumn(name = "ID", referencedColumnName = "ID"),
        @JoinColumn(constantValue = "A", referencedColumnName="type")})
    //              ^^^^^^^^^^^^^^^^^^^  I AM LOOKING FOR SOMETHING THAT DOES THIS.
    //                                   constantValue IS NOT A VALID ARGUMENT HERE.
    private TypeA inspectionSnapshot;
    @OneToOne(mappedBy = "owner", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
    @JoinColumns({
        @JoinColumn(name = "ID", referencedColumnName = "ID"),
        @JoinColumn(constantValue = "B", referencedColumnName="type")})
    private TypeB inspectionSnapshot;
    /* Getters & Setters ... */
}
@Entity
@Table(name = "TYPES")
@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name = "TYPE", discriminatorType = DiscriminatorType.STRING)
public abstract class BaseType {
    @Id
    @OneToOne
    @JoinColumn(name = "OWNER_ID", referencedColumnName="ID")
    private Owner id;
    @Id
    @Column(name = "TYPE")
    private char type
    /* Getters & Setters ... */
}
@Entity
@DiscriminatorValue("A")
public class TypeA extends BaseType {
    /* All functionality in BaseType */
}
@Entity
@DiscriminatorValue("B")
public class TypeA extends BaseType {
    /* All functionality in BaseType */
}